A technology has been proposed in which the pupil or the iris and a Purkinje image indicating reflection on the cornea are detected from an eye region in an image resulting from photographing the face of a person, and the person's line-of-sight is detected based on the positional relationship between the detected Purkinje image and the center of the detected pupil or iris.
For example, Japanese Laid-open Patent Publication No. 2000-070225 discloses an eyeglass-type line-of-sight detecting device having a light projecting element and an image capture element whose positions are fixed relative to the eyeballs of a person. In this scheme, when the eyeglass-type line-of-sight detecting device fails to detect a Purkinje image during detection of the person's line-of-sight, it detects the line-of-sight by using a Purkinje image detected in advance.
For a line-of-sight detecting device that detects the line-of-sight direction of a user of a computer or the like, for example, a display apparatus coupled to the computer or the like or a display unit of a smartphone, tablet terminal, or the like is provided with an image capture element and a lighting element. In such a line-of-sight detecting device, there is a possibility that the positional relationship between the image capture element and the lighting element and the eyeballs of a person varies. In addition, in such a line-of-sight detecting device, when external light, light radiated from a display apparatus, or the like is reflected on eyeglasses worn by the person, it is difficult to detect the position of the pupil in some cases. When the positions of the pupil and a Purkinje image that are detected in the state in which external light or the like is reflected on the eyeglasses are used for processing for determining the line-of-sight direction of the person, an error occurs in the detected line-of-sight direction of the person.
Accordingly, for example, Domestic Re-publication of PCT International Publication for Patent Application No. 2011/158463 discloses a line-of-sight detecting device for reducing determination errors in the line-of-sight direction. The line-of-sight detecting device stops processing for detecting the line-of-sight, upon detecting the occurrence of reflection of external light or the like on eyeglasses, and performs the processing for determining the line-of-sight when there is no reflection of external light or the like.